Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
You're mostly likely to trigger a dense, 2-5 foot thick slab avalanche on slopes facing the northern 2/3 of the compass, where the wind frequently blows, and the snowpack depth is variable. Avalanches are easier to trigger in thin spots at the edges of slabs. Here are some characteristics of suspect slopes:
- Wind-pillows, and textured surfaces where the wind has moved snow
- Rocks sticking out of the snow and wind-scouring along mid-slope gullies
- Terrain steeper than about 35 degrees. Slides most likely wheresome part of the slope is at least 35 degrees.
Remotely triggering an avalanche from flat terrain near steep slopes remains a possibility. If you do trigger an avalanche, you probably won't observe obvious signs of instability like snowpack collapsing or cracking beforehand.
Additional Discussion: Loose snow avalanches are possible on very steep slopes facing the sun. These often initiate near exposed rocks. Most will be small, but some may grow large enough to bury you beneath large slopes and in funneled terrain. You can reduce your risk by limiting your time spent beneath sun-drenched slopes that look like this, especially during the heat of the afternoon.
(12/31/2024) Large Persistent Slab avalanches like this one are possible at middle and upper-elevation terrain, especially in wind-affect areas or areas harboring a shallower snowpack.
